ON FRIDAY THE 13th, there came good news from the north for residents of the District of Columbia. Rhode Island, the 13th state to ratify the U.S. Constitution in 1790, became the 13th state to ratify the D.C. Voting Rights Amendment. This amendment, as people who live here know only too well, is the congressionally approved provision to let the home-town population of Washington be represented in Congress the way other Americans are. And though ratification has been agonizingly slow over the years since the amendment first cleared Congress, the pace has quickened.

Though it's a trifle early to be cheering the arrival of federal democracy in America's last colony, this is the third ratification this year. That puts the count one-third of the way toward the 38 state approvals needed by August 1985. With the kind of grass-roots understanding that people in Rhode Island showed in supporting the amendment, maybe other state legislatures will see the justice in following suit.

Jim Sullivan, a Rhode Island Common Cause member who worked for passage there, reports that it was this simple matter of fairness that guided his state's legislators to an overwhelming vote for ratification. The count was 74 to 6 in the state house and 33 to 7 in the state senate. The victory, he says, was "one where the injustice of Americans not having congressional representation outweighed any other objections. The Rhode Island legislature voted on the merits of the issue."

That's all that should have to be said on behalf of the amendment--without regard to the color, party affiliation, occupations or proximity to the Capitol building of the men and women who live here. They merely seek to participate in the decisions by which they and others across the country must live--from making war to raising taxes.

Washingtonians are counting on the continued understanding and reaction of fellow Americans to see the amendment through.